A click here, a mouse drag there—it adds up quickly. Now Illustrator lets you make your workspace more efficient by organizing your tools into custom panels:
I really like the ability to unbury certain tools (e.g. various shapes), especially as I’ve kinda never forgiven Illustrator for changing the way keyboard shortcuts work circa AI9. (In Photoshop, Shift+letter lets you cycle among tools that share that letter. In Illustrator, you can assign Shift+letter to a specific tool. Some people swear by one approach & some by the other.) I know, it’s been nearly 15 years, and I deeply need to get a life. (How am I not typing this from my parents’ basement?)
As for the inevitable, “So, where’s this feature in Photoshop?,” you can maybe blame me. I didn’t want to do just toolbar customization, or do it in just Photoshop. Rather I wanted to let people remix nearly any UI elements together (tools, menu items, etc.) and do so across apps. That’s where Adobe Configurator came from. Hundreds of thousands of people downloaded it, but only a few used it to create & share toolbars & other custom panels. Maybe I let the perfect be the enemy of the good, and I need to write up a post-mortem on that.